Process for treating carnallite bearing materials



' Aug. 2 0, 1963 F, sERowY v 3,101,247

PROCESS FoR- TREATING CARNALLITE BEARING MATERIALS Filed June'll, 1959INVENTQR FR/ TZ sERo wY A; CIAA met A frm/VE Y 5 arenas? sa conversionwhich takes place according to the yfollowing equation:

bischolite being additionally deposited. The resulting sultul'ic acidreacts in a lsubsequent hydrogen chloride eX- pulsion step of theprocess at temperatures above 40 C., notably above 90 C., lwith MgCl2still present, again forming MgSO4. Upon attainment yof the lsaturationlim-it it is deposited exclusively as a reactive kieserite depending onthe inconstant equilibrium of the continuously forming solution. Withrthis satisfactory :separation of the chlorides from the sulfatos, theabove-mentioned prior art process step of precipita-tion of themagnesium sulfate by means cf calcium salts and the removal lof theresul-ting calcium -suliate becomes unnecessary. Y

All partial processes within the principal-process proceed atpredetermined temperatures in the range between `and 100 C. Hence, inthe expulsion of the hydrogen chloride more highly compressed steam isnot required, but cheap waste steam sullices which, Vfor example, maycome from :the power `generation rior operation of the entire plant. Inaddition, there `is needed in the cycle besides the heat for heating thesolution, only beat of evaporation tor the hydrogen chloride used andminor amounts of water according to the partial pressure 'above thesolution. in contrast, in the usual evaporation processes of the priorart the entire water of the mother liquor excepting the 4hydrate waterof the bischoite would have to be vevaporated for recovery of the solidsalts. There is, calculated vfor the HCl evaporation and a little wateras cornpared with of the total water, .a calorie saving of at least 35%and of course accordingly less when heat recovery takes place in thelatter case.

The expulsion of the hydrogen chloride following the sal-ting-out of thebisohoite is effected by a known process.

The resulting rock salt and more or less kieserite bearing residueincluding mud -f-rom the dissolving step of the oarnallite and-kieserite bearing mineral salt can be likewise processed in .a sideprocess with hydrochloric acid of 'about 12% HCl and more to lform areactive niagnesium sulfate hydrate. It can, in fact, be dissolved outof the residues including mud by means of hydrochloric acid withoutatt-ack of the rock salt and appreciable double salt .formation and be`salted out jas kieserite at temperatures above 40 C. after furtheryaddition or hydrogen chloride, At temperatures below 30 C., when thesaturation limit is reached, sulfuric acid is formed with separation ofbischolite, as mentioned above. The recovery of the entire -kieserite.from the crude salt would thus be possible in combination with thesalting-out process of the mother liquor from the crystallization otpotassium chloride or without the same. Moreover, at the same time thewash liquor problem is radically solved.

As a precaution, Vthe resulting mother liquors of the carnallitedissolving process may be debrominated beforeV being salted -out.asVhydro-gen chloride liberates elemenn tary bromine in smal-l amounts fromthe bromide salts through Ia pllotochemical react-ion. l

The importance of the total lprocess resides in the possibility oftreating carnallitic and kieserite mineral Asalts of oceanic originwithout any linal liquor discarding (mother liquor as well as wasteliquor), in a substantial increase invention can be combined andemployed `with other processes or parts thereof under observance of theprinciple l set lforth.

The following examples are lfurther illustrative of the presentinvention and it will be understood that the invention is not limitedthereto.

Example l vfrom which solid products are continuously removed but fromwhich no liquid is discarded. The necessary water for the system can beintroduced at any suitable point in the system. Thus, in one form of theinvention the necessary water may be introduced atV vessel V where it isused konly once to treat the carnallite rock. Subsequent chargesofcarnallite rock,'lrowever, are treated with the liquor that is formedwhen the system reaches equilibrium. Thus, subsequent charges ofcarnallite rock together with the deposited carnallite and NaCl fromvessel il are introduced into treating vessel V wherein they are treatedwith liquor coming from a previous step of the total process andcontaining below about`l6% HC1l down to 1% HC1. The carnallite rock aso.is mixed with the mother liquor at a temperature :of about 90 C. Thismixing and especially the driving off ofv HCl lis aided by a mild streamof air that is injected into vessel Y. HCl con.- tained in this liquoris distilled together `with lan amount of :Water which corresponds tothe prevailing partial pressures in dependence on the continuousdissolution of magnesium chloride from carnallite, and on thetemperature, and is condensed in redux condenser VI. The liquorcontaining the residue and line salt-containing mud of carnallite rock,consisting of rock salt, kieserite aso. is conveyed to tank Vll where itis stirred once more and the small amount of HC1 (at most 1%) isneutralized with limestone lor magnesite (dolomite). The undissolved.coarser material settles to the bottom of the tank Vll and is removedas residue or moved on for Vfurther processing to recover kieserlte. Thehot carnallite solution is then conveyed to clarification tank Vil-l ina manner known per se where further insoluble materials (mud containinglinesalt) Vare removed. The clarified solution of carnallite is thenconveyed, in la conventional manner, to vacuum cooler iX through linelr6. Liquor recovered from lter XH after removal yof mud is alsoconveyed to the vacuum cooler through line d3. The carnallite solutionwith thecrystallizeld product KCI is then carried to settling tank X.Mother liquor from settling tank X (by line 14) and liquor obtained inlilteningthe crystals in filter Xi (by line 15) is conveyed to'tank I bymeans of pump P.

The mother liquor flowing in line 14 is substantially an aqueoussolution containing yamong other things MgCl2, KCl, NaCl, MgSO4. Thisliquor contains under optimum conditions at 20 C. alittle more than 300g./l. of MgCl2 introduced into tank V. This'treatment'takes place vat oithefpotassium chloride yield up to v93% and more (to about 100%), and inan improvement oftheV quality of the special products bischoliteas'chemical component of carnallite and kieserite obtained byselective-.separation andfrepresenting valuable basic Ymaterials of thepotash industry. v Y

lPhe rock salt and insoluble impurities from the residues (includingmud) stay behind yand may be used as mixing material in the mine or forpreparing the ybrine for the salt recovery.

In the accompanying drawing the process `of vention is represented inprinciple.

the -in- The process oi the and about 410 g./1. of KCl. Y

The mother liquor enters tank I and there it is treated with -a smallamount-of gaseous HC1 escaping yfrom vessel li by means of line 20 andthe HC1 gas carried over froml refluxl condenser VI through line 21 bymeans `of the air a temperature of from '20 to 309 C. The air is removedfrom the system by means of line 22. The concentration .of HClwin tank Iis Vmaintained at a maximum kof about The liquor -is then conveyed' totank AlI by: means Vof line23. The solution `is cooled to below 20 C andtreated with HC1 gas coming from tankII-Il by Way of line 24. Moreover,la little concentrated hydrochloric acid normally overflowing from HClstorage vessel XlII isfed to tank H via line 25. The concentration ofHCl is main- Under.

tained in tank Hat more than 12% to about 15%. this condition,carnallite and NaCl areseparated, whereas MgSOl remains in solution. YThe precipitate is lcontinuously removed by line 33 over saltseparators, iiltered and transferred by line 34 kto tank V forretreatrnent.

.The solution from tank II, practically free from alkali chloride, iiowsinto tank III by'way of line 26. Hydrogen chloride low Vi-n watercontent is introduced by line 27 from the vapor Zone of tank IV afterpassing through the HCl storage tank XIII. The -solution is cooledsharply to room temperature |and below, i.e. below 20 C., anrd theconcentration of I-ICl is maintained at about 20%. As a resul-t of thetreatment, technically pure bischoiite is precipitated inexactly thesame quantity as MgCl2 Was introduced with carnallite land iscontinuously removed by line 28 to salt separators and filters. VTheliquor remaining behind in tank III still contains about of MgCl2. Themagnesium sulfate is still-in solution. If the concentration of MgSO4should increase beyond the saturation point, there would occur areaction with hydrogen chloride forming magnesium chloride and sulfuricacid, the former separating as bischote.

The solution from tank III il-ows to tank IV through line 29. 'Iheliquid is heated in tank IV to a temperature of 95 C. and above bycirculation preheating. The hydrogen chloride from this tank isdistilled in concentrated form (about 95% HC1) through line 27 so thatabout 16% HCl remain. Any sulfuric acid formed in tank III reacts intank IV with a part 'of the residual magnesium chloride present underthe-conditions prevailing in'tank IV, whereby MgSO4 is formed. Thistogether with other MgSO4 that may be present in the system isprecipitated as kieserite (MgSO4-H2O) on reaching the salting-out point,in tank IV and removed through line 30- by a salt separator. and latilter. The hot hydrochloric acid solution which is low in HCl contentliows from tank IV to tank V through line 31.

off with the aid of elevated temperature and la mild air lstream throughline 32 vto a reilux ycondenser VI where it is condensed and stored inHCl storage tank XIII for use in the process. The HCl-concentration inthe liquid remaining in tank V decreases to about 1% I-IC-l and is usedto treat a new charge 'of carnallite rock, as well-as carnallite andNaCl from step II. The cycle is thus completed and there is no dischargeof liquids. Y

An example of the normally continuously conducted process will show thefollowing Ailow rates, without consideration of the residue utilization(Example -2) underthe condition that Vant Hoffs equilibrium solution(Q20 C;) is reached for the mother liquor. A

The temperatures or the temperature'lranges correspond to the onesindicated above andithey may be varied, i.e., may be higher or lowerwhen other conditions are varied f in the treatment of carnallite rock,as often occurs.

43.0 tons/hour or about 10'00 tons/day of crude carnallite (53%KCl.MgCl2.6I-I2O, 15% MgSO4.I-I2O, 32%

NaCl insoluble matter disregarded) are conveyed to treatl ment step tankV together with 15.4 tons'of the chloride mixture salted-.out in vesselII (containing 10.5 tons carnallite, 0.7 ton bischoiite, 2.7 tons NaCl,l1.5 tons adhering solution).v The remaining hydrogen chloride of thesolution vfrom step IV escapes with an amount of water vapor 10-40% H20)corresponding yto the partial 'pres- KCl, 0.7 ton NaCl, 0.7 ton adherentsolution) and 100 tons'mother liquor (2.8% KCl, 25.2% MgCl2, 1.0% MgSO4,2.7% NaCl, 68.3% H2O). l

` From 100 tons per hour of the mother liquor,` 15.4 tons chloridemixture of the above vgiven composition are salted out at temperaturesbetween 20 and 30 C. by means of 15.2 tons hydrogen chloride from thevapor zone of vessel III and, to a small extent, by means ofconcentrated hydrochloric acid fromlthe I-ICl'storage vessel XIII. The4100 tons intermediate solution remaining in Vessel'II (15;0% HC1,21.0%`Mg'Cl2, 1.0% MgSo4, 63.0% H2O) pass'over to the treatmentvesselIII. They are further salted yout by additionof2L9 tons HC1 (practicallyanhydrous) from the V'apornon ofthe-HC1 storage vessel XIII, attemperatures betwe'e'nflS and 20 C.l yThe result are 18.5`tons bischote(16.7 tons MgCl2-6H2O, 1.8 tons adherent solution). Furthermore, 86.0tons intermediate solution remaining inivessel III (20.8% HCl, v

15.2% MgCl2, 1.0% MgSog, 63.0% H2O).

84.2 tons per hour of this intermediate solution of the composition asdescribed, are heated in treatment vessel IV by circulation heating totemperatures above 95 C., while at the same time 4.7- tons 95 HCl aredriven over to the HC1 storagevessel XIII. In vessel IV there remain80.0 vvtons intermediate solution (16.0% HCl, 16.1%

MgCl2, 0.9% Mgsog 67.0%. H20). Kiest-.rite dees not separate, since thesalting-out point for `MgSO4 is not'yet reached; however, this may occurif the liquor circulation is combined with residue treatment. 80.0 .tonsper hour of hot intermediate solution, of a composition as describedabove, are flowing iinally to treatment vessel V." There,

' 43.0 tons/hour carnallite rock (composition. as above) are Here theresidual I-ICl is driven :vapor pressure sures of the weakly `acidiccarnalli-te solution (about 1% HC1, temp. above 95 C. to near boilingpoint). The water which evaporatedandwas condensed,y in-rellux con`conc. HCl overflowing -`rfrom 'HCll storage tank' XIII.

Formed are: `107.5 tons/hourfhot solution (8.3%KCL 23.6% MgCl-2,10%MgSO, 3.2% NaCl, 62.9% H40) l i land 208`tons residue (6A-tonskieserite, 12.3 tonsrock denser'VI returns into thprocess at VIIlbyrneans of the introduced at the temperature of above 9.0 C., Aand'15.4tons/ hour of the chloride mixture which was salted out in treatmentvessel II. A slight current ofair serves-for better stirring and forexpelling hydrogen chloride'duning the-dissolution of magnesium chloridein the/solution, which takes place in a few minutes.V During vthis step,

14.2 tons-HC1 escape in a condition comparatively rich in waiter,entering the rellux condenser VI.

Some small discrepancies in -the computation of the balance ofmaterialsfwhich in large-scale operation can easilybe compensated,result from the naturalV iluctuations in the composition of the startingmaterials `and in the inconstant equilibrium conditions of the solutionand the ratio rH2O:IIC1 vary-ing with the temperature. l

Example 2 'Ihe residue andthe mud from the hot `solution-are treated inone lor more settling vessels XIV equipped with l sieve bottoms,'oncewith hydrochloric acid of more than 12% HC1 content in codirectional orcounter flow. The kieserite dissolves readily, favored by simultaneoushydration, and increasing temperature lto 40"v C., up to a concentrationof more than,25% MgSO., in solution; The y rock salt and otherAsecondary components,` anhydrite,

clay, etc. arewattac'ked but slightly. Formation of double salts ldoesnot take place.l

The residue is removed lafter filtration over line 38. It consistsoffrock salt in amore or less pureV condition. In

'further charges of kieserite, mother liquor from ,aA subse- I quenttreatment operation XVI is used as solvent which is. supplied throughline 35 to1-.ves'sel XIV ,under cooling. The solution obtained-in vesselXIV is passed through line v 36 to vessel XV. By supplying hydrogenchloride,k with llow w21-'9er contents fromjthe vapor space ofthecollectingves-Av sellfof condensatio'nsystem VI over line39gff'apureyery' ne-grainedikiesetelis saltedfoutnwith util'il'zation ofthef-yconsiderable'V amount'of Vheaty of condensation, a't temper-.1

atunes 'above 40Y'C., which is separated lover line 37 in f saltseparators and :il-.teredV Thegremaining solution coni tainsvat atemp-eraturelof` 40760C. and a vconcentration in 4the vacuum coolingstep and water return over the cry's-` tal-purilircation sten-7.5 tonscrystallized matter (6.1 tons .of about 22% HC1, sun about vv16% Mgsoi.Y ruis serution is passed over to vessel I. By raisingtheftemper-yvsacre/ia' ature to over 90 C. a larger portion iotHCl is distilled offand ilows through line 40 into the HC1 storage vessel XIII. Theremaining solution is passed over 35 under cooling to vessel XIV. Thecyclel of the movement of liquors and of hydrogen chloride is therebyclosed.

20.8 tons/hour of residue (from Example l, composition as above) aretreated at about 40 C. in a countercurrent process with 35.2 tons ofcooled diluted magnesium sulfate solution (16.1% HC1, 2.8% MgCl2, 19.0%MgSO4, 62.1% H2O) supplied from the vessel XVI.' The results are: 45.6tons concentrated magnesium sulfate solution (12.5% HC1, A2.4% MgCl2,28.0% MgSOi, 57.1% H2O), furthermore 14.0 tons impure rock salt (12.4tons NaCl, 0.2 ton KCl, 1.4 tons adherent solution).

After this solution has been passed to vessel XV, 3.6 tons/hour of HC1poor in water are admitted from tx e vapor space of the HC1 storagevessel X111. When the salting-out point is reached at temperaturesbetween 5G and 60 C., 7.1 tons kieserite (6.4 tons MgSO4-H2O, 0.7 tonadherent solution) are salted-out. 40.7 tons diluted magnesium sul-fateintermediate solution remain of the following composition: 22.0% HC1,2.4% MgCl2, 16.5% MgSO4, 59.1% H2O.

From this solution, 5.5 tons hydrogen chloride containing 40% H2O areexpelled by raising the temperature to 90-100 C.

The remaining 35.2 tons magnesium sulfate solution ofthe above indicatedcomposition, are cooled down to a temperature of 30-40o C. and are usedfor treating 20.8 tons of fresh residue in a cycle process.

While the invention has been described with particular' reference ytospecific embodiments and examples are given on the quantitative courseof the process, it is to be understood that it is not limited thereto,but it is to be construed broadly and restricted solely by the scope ofthe appended claims.

What is claimed is:

1.- Acycllc process for the treatment of a carnallitebearing materialfor the recovery of KCl and other mineral `salts therefrom without`formation of a liquor which must be disposed of, which comprises mixingin a first zone said carnallite-bearing material with la dilute MgCl2-containing HC1 solution of about 1% HC1 produced in a previous step inthe cycle and treating it ata temperature of about-90 C., whereby asolution is produced containing KCl, NaCl, MgCl2, and MgSO4;neutralizing small amounts of HC1 in said last-mentioned solution by anequivalent amount of alkaline material, removing from said neutralizedsolution residual solids and mud; thereafter crystallizing the mainamount of KCl by a cooling operation and removing the crystals in pureform from said solution, thus leaving behind a mother liquor containingMgCiZ, lvigS-Oi, NaCl and residual KCl; passing said mother liquor to asecond zone wherein said liquor is stirred with HC1 to a concentrationof about 1% HC1 in solution at a temperature of about 20-3C- VC.;precipitating from said mother liquor in a third zone carnallite andNaCl by treatment with approximately 12-15 HC1 solution at a temperatureof about 20 C., leaving MgSOi in solution; removing said carnallite andNaCl for retreatment together with new carnallite-bearing material;cooling in a fourth Zone said MgSG-containing solution to a temperaturebelow 20 C. and increasing the HC1 content to about Ztl-30%, therebyprecipitating pure MgCl2-6I-12O and removing the crystals from thesolution; heating the last-mentioned solution in a fifth zone to atemperature of about C. and evaporating the HC1 content to about 16%,whereby l-gSO4-H2O is precipitated, removing the same from the solutionfor recovery and using the solution from the above-dened,

step-Wise separation of salts for treating in said irst zone freshcarnallite-bearing material thereby closing the cycle, while recoveringKCl, NaCl, MgCl2-6l-I2O and from the respectivezones in said separateoperations.

2. A process according to claim 1 including the step of introducing amild stream of air into the rst zone of operations.

3. A process according to claim 2 wherein HC1 expelled in the iirst andlith zones is condensed and recycled to zones 2, 3 and 4 in the process.

4. A process according to cl fm 1 including the steps of separatingresidual solids and mud whichy contains iinely divided salts consistingof ltieserite, rock'salt and impurities from the hot solution, formed insaid first Zone, extracting said residue and mud with 12% HC1 solutionwhereby the kieserite dissolves, salting out said kieserite from saidsolution with concentrated HC1 whereby a rest of about 19%unprecip-itated MgSO4 is-left in solution, conducting this solution tosaid fourth zone, precipitating bischoiite in said fourth zone anddistilling HC1 contained in the liquid of said zone.

Reierenees Cited in the le of thispatent UNITED STATES PATENTS.1,801,661 Coll-ings ApifZl, 1931 1,336,426 Allen Dec. l5, 19312,687,339 Dancy Aug. 24, 1954

1. A CYCLIC PROCESS FOR THE TREATMENT OF A CARNALITEBEARING MATERIAL FORTHE RECOVERY OF KCI AND OTHER MINERAL SALTS THEREFROM WITHOUT FORMATIONOF A LIQUOR WHICH MUST BE DISPOSED OF, WHICH COMPRISES MIXING IN A FIRSTZONE SAID CARNALLITE-BEARING MATERIAL WITH A DILUTE MGCI2 CONTAINING HCISOLUTION OF ABOUT 1% HCI PRODUCED IN A PREVIOUS STEP IN THE CYCLE ANDTREATING IT AT A TEMPERATURE OF ABOUT 90*C., WHEREBY A SOLUTION ISPRODUCED CONTAINING KCI, NACI, MGCI2, AND MGSO4; NEUTRALIZING SMALLAMOUNTS OF HCI IN SAID LAST-MENTIONED SOLUTION BY AN EQUIVALENT AMOUNTOF ALKALINE MATERIAL, REMOVING FROM SAID NEUTRALIZED SOLUTION RESIDUALSOLIDS AND MUD; THEREAFTER CRYSTALLIZING THE MAIN AMOUNT OF KCI BY ACOOLING OPERATION AND REMOVING THE CRYSTALS IN PURE FORM SAID SOLUTIONTHUS LEAVING BEHIND A MOTHER LIQUOR CONTAINING MGCI2, MGSO4, NCAI ANDRESIDUAL KCI; PASSING SAID MOTHER LIQUOR TO A SECOND ZONE WHEREIN SAIDLIQUOR IS STIRRED WITH HCI TO A CONCENTRATION OF ABOUT 1% HCI INSOLUTION AT A TEMPERATURE OF ABOUT 20-30*C., PRECIPITATING FROM SAIDMOTHER LIQUOR IN A THIRD ZONE CARNALLITE AND NCCI BY TREATMENT WITHAPPROXIMATELY 12-15% HCI SOLUTION AT A TEMPERATURE OF ABOUT 20*C.,LEAVING MGSO4 IN SOLUTION; REMOVING SAID CARNALLITE AND NACI FORRETREATMENT TOGETHER WITH NEW CARNALLITE-BEARING MATERIAL; COOLING IN AFOURTH ZONE SAID MGSO4 CONTAINING SOLUTION TO A TEMPERATURE BELOW 20*AND INCREASING THE HCI CONTENT TO ABOUT 20-30%, THEREBY PRECIIPITATINGPURE MGCL2.6H2O AND REMOVING THE CRYSTALS FROM THE SOLUTION; HEATING THELAST-MENTIONED SOLUTION IN A FIFTH ZONE TO A TEMPERATURE OF ABOUT 95*C.AND EVAPORATING THE HCI CONTENT TO ABOUT 16%, WHEREBY MGSO4H2O ISPRECIPITATED, REMOVING THE SAME FROM THE SOLUTION FOR RECOVERY AND USINGTHE SOLUTION FROM THE ABOVE-DEFINED STEP-WISE SEPARATION OF SALTS FORTREATING IN SAID FIRST ZONE FRESH CARNALLITE-BEARING MATERIAL THEREBYCLOSING THE CYCLE, WHILE RECOVERING KCL, NACL, MGCL2.6.2O AND